https shouldn't be required.
Applets and Java Web Start will stop being supported this year or maybe next year in the best case. Several web browsers will drop the support of the NPAPI which is used in all implementations of the Java plugin. Anyway, they are already very difficult to use. If you don't plan to buy a certificate, don't waste any time in trying to sign your JAR, only OpenJDK users will be able to run your applet without having to modify the default security settings.
There are a few alternatives. You can make a standalone application packaged with IzPack. You can make a single "executable" fat JAR runnable with a simple double-click (except when the default archiver opens it) or you can wrap such a JAR into a native application bundle. I use the very last solution under Mac and I'm going to do the same under other operating systems.